Checking cutter teeth



ADS 1953 c. H. cARLoN 2,846,773

CHECKING CUTTER TEETH 'mled'reb- 41. 1957 v 7 sheets-'sheet 1 AMPLI Fl E R JNVENTOIL Caro? H. Car/Son Aug. 12, 195s C. H. CARLSON CHECKING CUTTER TEETH '7 Sheets-Sheet 2 Filed Feb. 1, 1957 BY callan,

Mr RLw/w fm w@ .im W 0 X ww ATTORNEYS Aug. l2, 1958 y c. H. cARLsoN CHECKING CUTTER TEETH 7 sheets-Sheet s' Filed Feb, 1, 1957 as" N INVENToR. Cam? H. Carisa/z aib,

ATTORNEYS Aug 12 1958 I c. H.` CARLSON 2,846,773

cHEcKING CUTTER TEETH Filed Feb. 1. 1957 '1 sheetssheet 4 ggf. la.

49 INVENToR.

J5@ Caro? H. Carlson 55 BYCQLA, fw.;

. ATTORNEYS Agg. 12,1958 c. H.AcAR| soN CHECKING CUTTER TEETH 7 Sheets-Sheet 5 Filed (Feb. 1, 1957 JNVENToR. 0am/ A! brisa/I ATTH/VEYS Ag 12, 1958 c. H. CARLSON Y 2,846,773v

cHEcKING CUTTER TEETH y Filed Feb. 1. 1957 v sheets-sheet e :Nm/Tm Caro? M 'Carlson A T'TRNEY United States Patent() CHECKING CUTTER TEETH Carol H. Carlson, Rockford, Ill., assignor to Barber- Colman Company, Rockford, Ill., a corporation of Illinois Application February 1, 1957, Serial No. 637,717

7 Claims. (Cl. :i3-179.5)

This invention relates to a machine for checking the location of the sides or flanks of the teeth arranged in a row in a multiple tooth cutter such for example as a hob. The invention has more particular reference to checking of cutter teeth by sensing dimensional variations through the use of a feeler engaged and moved by the passing teeth. In cutters of this character, the teeth are usually arranged in a plurality of parallel rows so that opposed sides of the teeth of adjacent rows constitute the walls of an intervening groove paralleling the tooth rows.

The primary object is to provide a checker of the above character in which two cutter tooth sides are felt of and checked dimensionally in a single pass through a feeling position.

A more detailed object is to feel of the oppositely facing tooth sides successively by two feelers arranged in a novel manner for engagement one at a time with respective tooth sides.

Another object is to bring the tooth sides into engagement with the feelers in a novel manner so as to simultaneously check several positional characteristics of the cutter such as lead, run-out, wobble, etc.

The invention also resides in .the novel mounting of the feelers and in the manner of amplifying and recording their movements.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which Figure 1 is a plan view of ya preferred form of cutter checking machine embodying the novel features of the present invention.

Fig. 2 is a fragmentary end view of part of a cutter to be checked.

Fig. 3 is a fragmentary elevational view of the front face `of one of the cutter teeth.

Fig. 4 is a fragmentary development View of part of the cutter teeth.

Figs. 5 and 6 are similar development sectional views taken along the arcuate line 5 5 of Fig. 2.

Fig. 7 is a diagrammatic view illustrating the various feeler movements.

Fig. 8 is a schematic view of the cutter drive and feed mechanism.

Fig. 9 is a vertical sectional view taken along the line 9 9 of Fig. 1.

Fig. 10 is a fragmentary plan view of the mechanism shown in Fig. 1, the cutter being shown in section.

Fig. 11 is a fragmentary section taken along the line v11-11 of Fig. 10.

Fig. 12 is a fragmentary section taken along the line '12-12 of Fig. 11. I

Fig. 13 is a fragmentary perspective view of the feeler or position sensing mechanism. f

Fig. 14 is a schematic view and partial wiring diagram of the displacement magnifying and recording mechanism.

Figs. 15, 16, 17, 18, and 19 are charts produced in the "ice testing of different cutters in accordance with the present invention.

Fig. 20 is a perspective view similar to Fig. 13 showing a modified arrangement of the feelers.

Fig. 21 is a diagrammatic view similar to Fig. 7 and illustrating the action of the modified feeler arrangement.

The invention is illustrated in the drawings as a ma chine and method for automatically checking several dimensional characteristics including the lead on both sides of the teeth of a hob 10 and simultaneously recording variations in these characteristics. A cutter of this type comprises a row of teeth 11 extending along a helical center line 12, usually through several revolutions, around the hob body 13, the angle h (Fig. 6) of the helix being known as the lead angle. Each tooth has a cutting face 14 conforming in cross section to the interdental spaces of the gear to be generated by the hob` so that opposite side edges 15 and 16 (Figs. 3 and 5) of each facecon-` verge outwardly from points 17 onthe pitch line of the tooth.k To maintain the same contour of the teeth lafter each sharpening by grinding away the faces 14, the hob teeth are backed off that is, the top surface 18 of each tooth, although of uniform width as shown in Fig. 4, is curved inwardly toward the hob axis (see Fig. 2) and away from a circumference 19 through the tip of the cutting face. The pitch lines 20 along the tooth anks 21 and 22 are similarly curved inwardly so that, as shown in Fig. 5, the longitudinal section of each tooth taken along a circumference 23 (Fig. 2) concentric with the hob axis through the pitch points 17 at the cutting face 14 tapers away from this face in a direction reverse to the direction of rotation of the hob in service use.

ln adapting the present invention lto the checking of hobs, advantage is taken of this back off characteristic to enable oppositely facing side edges 15'and 16 o f the cutting faces 14, either of the same tooth or the teeth of adjacent rows, to be engaged and felt of successively and variations in the positions of these edges relative to the h-elical path of travel thereof to be sensed in a single pass of the cutter teeth past a feeling unit 24. Such `feeling of the tooth anks is effected by feeler elements 25 and 26 which, in the preferred form shown in Figs. 1 to 19, are disposed on opposite sides of a helical center line 12 and mounted on a common support movable transversely of such line to enable the elements to engage the anks on opposite sides of a tooth passed between the feelers. At the same time, the feeler elements are spaced apart by an amount a (Fig. 6) longitudinally of the line 12 for successive engagement with the tooth edges 15 and 16 and also transversely of the line a distance b (Fig. 4) slightly less than the width of the cutting faces 14 at some predetermined point 17 along the edges such for example as points along the pitch line 20.

The hob is rotated and fed axially as indicated by the arrows in Figs. 6 and 7 to advance the teeth along the center line 12 and present the side edges 15 and 16 rst to one feeler 25 and then the other 26 whereby one feeler is cammed outwardly while the other is out of engagement with the hob tooth. The successive movements of the feelers are amplified and recorded as marks 27 and 28 (Fig, 7) arranged in rows of a traveling tape 29 (Fig. 1) for ready comparison with each other.

While being checked in the above manner, the hob 10 is fastened on an arbor 30 supported at opposite ends in tail and head stocks 31 and 32 mounted on a table 33 slidable longitudinally of the arbor along guides 34 on a bed 35 housing a drive motor 36. Through suitable chain and gear connections 36a including pick olf gears, the arbor may be turned at the speed desired for presenting successive teeth of the hob to the feelers 25 and 26. At the same time, the motor operates through suitable gearing- 37 including al manually shiftable clutch and-pick-oi-gears' toturn a lead -screw- 38 and thus advance a nut 3:8a and the table 33 at a rate corresponding to the lead of theteeth on the hob being checked. Theteethtare-thus -presented toithe -feelers successively and in precisely centered relation with respect to the center-line -121' For set'up-purposesfthehob may be turnecl independentlyfofl the lead-screw nby manipulating ahand wheel-391g- Thel feeler-unit 24is supported on themachine base 35;'for-adjustmentin various -ways 'and includes the feelers-2A5andg26whieh may-take thevformof small balls. Herein -these- -ba-lls1-are attached to the ends of rods 40 projecting-frontend-detachablyclamped by screws 41 in -the --ends-of-elongated'-levers 42 and 43--lying alongside-each-` other-and-fulcrumed-intermediate their ends una pin 44--(1`ig.\ -11)' whose/ ;.opposite endsA are pivoted on--cerxter-points4S.-on.-alpost 46 `upstanding from a plate-474;-Thelatter-isheldlby--a headed screw 48 against the-top-of-aslidel 49- andy the-Y endremotefromV the feeler points,is-fulcrumed-on aV stud 50on the slide so that by swinging-of -the-platethe-feeler'unity may be adjusted in a direction-longitudinally vofthe hob axis. Under the action of-'a-y spr-ing 51, a projection-depending from the plate 47-2 is held-againsta stop 52 formedl by a screw 53vand-associatedvernier-screw54 carried by the slide 491 The latterv (Figs. 9 -and 11s)A is slidable toward and away from--thehob along-waysSS von the base 35, this adjustrnent--being-elected-through a rack 55a carried by a bracket-,SG-and meshing -with -a pinion 57 mounted on theslideand-operated by a hand knob 58'. The bracket is .fulcrumedatUSa on the machine base to swing about an-,axis-par-alleling-thevcutter arbor, the adjusted position beingretainedby a clampactuated by a handle 56h.

The Vfeelers-ZS andv 26, although mounted on the two part support-formed by--thelevers-42 and 43, may be adjusted-..relative-to eachother-laterally ofthe path of advance-.ofthe hob teeth -being checked but, during the actualffeelinglof the-teeth,V these feelers move together as a unitawayY fromand toward a normally centered position shown-itin: Fig. 4. Forthe-s'eparation adjustment, theharmsare-joinedby-a cross-screw-59 (Fig. 10) which projects lthrough --and -abuts againstthe arm 43 and threadsninto-.the `arm.42., A spring acting between the arms.- holds.thevarm43;against the head ofthescrew, the two.. arms .thus being joined-to swing in unison about the.piv.ot ,44;

Thetnormallycenteredy position of the feeling unit is determined bya stop 61.-.(Figs. 10,-11 and 13) in the form-.of-a;post.upstandingfrom-the plate 47 and coactingtwitha stud .,62-rigid-with.- and depending from a rearwardlyprojecting extension 63 of the arm 42. This pin istdisposedbetween.` two arms 64 and 65 ulcrumed on the..pivot44and projecting rearwardly therefrom alongsidegthe,extension..63.. A bowed spring 66 joining the alms,6.4;.and-.651` urges the latter toward each other so that, when vthe feelers and 26 are free, the-arms contact.y `oppositeucsides: ofthe stud61 and-also the pin 62. The, `feeler-unit is thus held in the centered position shown in1Figs.l0;sthrough l13. This positionmaybe adjusted laterally-ofthe feeler-.arms-throughA the medium of the screWsSfgand 54; above described.

Forthe ,purpose of .greatly magnifying the alternate 4..P ing 70 and inductively coupled with three windings 71, 72-and 73'enclosing and axially spaced along the plunger-.- The outer end 76 of the plunger 69 extends at right angles to the feeler arm extension 63 and is held in contact with the latter by a spring 77. The primary coils 71 and 73 are wound in opposite directions and connected in series so that the voltages induced; thereby in the secondary coil 72 exactly neutralize each otherwhenthe plunger is precisely centered relative to the windings. This condition maybe obtained by manuallyy turning a knob,.74

but `of opposite sign, Adis'placement sensing unit ofthe-- above character is manufacturedV by Br usl1 ,Elect1onicIk Company and known asV BL 306.V

The output from the transducer. may be magnified `by an electronic amplifier 79 which maytbe of well ,known construction such as Brush Electronic Company part No.

BL 309. The amplied voltage from the amplii/ ierisV applied to a suitable recorder 80 such as a magnetic direct inking oscillograph (Brush `Electronicpart BL 201);

which incorporates the usualV dArsonval galyanotneter.fonl swinging the indicator and recording arm 68 across-the continuously advancingtape 29 to record the marks 27 and 21 corresponding to the feelerl movements., Recorders of this characterrusually have an rauxiliary arm 81--(Fig. l) for recording other events in response tooperation of a switch 82. In this instance the Switchis operated by a cam 83 fast .on the cutter arbor and shaped to cause onemark '83a to beprodueed on thetape at a predetermined point in, each revolution ofthe cutter-` being tested. Thus the marks 27 and,28corresponding to a particular toothl` of the cutter may be identie,d

easily;

OperationA The machine shown intFigs. 1 to `19 operates as follows .f assuming-that the cutter whose' leador otherdimensional characteristics are to be checked is mounted on the arbor\ l30and thegearing-tiqand 37 Vis adjusted to correlate the .turning-(offy the cutterwith the correct lead. of the hob teeth. The latter are thus centered accurately onthe line.

12 asy ltheypass-the feelers 25 and. 26. kThe .cutter is turned in a direction opposite to that of service use,.

that is to say, with the-cutting faces-13` trailing so that the narrow leading ends 9010il the,v tooth sections iirst` enter between the-.two feelers.

To adjust the feeler unit to the particular.hob,=theslide `49 is adyancedj-.torthe-,hobby turning .the .handwheel 58 to bring the -Yfeeler' points 25; and .-26 4intoposition on. oppositesidesgof; one, tooth of -the hob, preferably at the pitch points 17. feeler 26, is moved intot'he path of a cutting face 14 and slightly inwardly from the side edge 16 so that the .feeler wil1-be. carnmedfoutwardly, as,the,edges of successive teeth pass it, these movements being indicated -byoutf' ward swinging of ,the A4stylusg, fthe,.extentof the-inward adjustment-of.the,feeler:being such that the stylus movement4 is abouthalfI the widthA ,of the. chart 29; The screw 59 is then adjusted to move the feeler 25-into a position forfsirnilar engagement. and.outward-movement by them cutting edges 15 and corresponding movementoflthe stylus backY and v.forth across the opposite side portion 4ofthe chart.

When-.itl becomes necessary to check the calibration of `the-.amplifier orrecorder,A the mirometernface 86"'is brought intol contact lwith the feeler arm 63 until a per- By turning the.screw- 53, lthe-A eptible movement is noted on the stylus of the recorder. The reading of the micrometer and the position of the pointer is now noted and the micrometer is adjusted by a fixed amount, for example .001 of an inch, and the extent of the movement of the pointer noted. By adjusting a calibration screw inside of the amplifier case, this calibration may be corrected, knobs 88 being used to control the amount of amplification and the positioning of the stylus.

'I'he entire apparatus now being conditioned, the hob is positioned with its terminal tooth ready to approach the feelers and the motor 36 is started to initiate the actual checking operation. The leading end of each tooth enters between the feelers 25 and 26 which remain out of contact with the flanks 21 and 22 until the tooth is approaching the position shown in Fig. 5 and has nearly passed the feeler 26. At this time, the flank 21 of the tooth at a point 90 (Fig. 5) engages the feeler 26 and cams in outwardly to the position shown in Fig. 5 just as the cutting face 14 of the tooth passes the feeler. At this time, the other feeler 25 is as shown out of contact with-the tooth ank 22 so that the feeler unit is free to move to the right as viewed in Fig. 5 and upwardly as viewed in Fig; 10, the plunger 69 being pushed a corresponding distance inwardly away from the normally centered position against the action of the spring 66. As described above, this displacement will be amplified and swing the pointer 68 outwardly away from the centerline 87 to produce a transverse mark 27a (Fig. 7) on the tape 29. When the edge of the cutting face passes beyond the feeler 26, the latter, together with the plunger 69 and the entire feeler support, will move inwardly and back to the centered position under the force of the spring 66. The pointer 68 thus moves reversely to form the other part 27b of the first mark 27.

The feeler 26 is now free and is disposed opposite the space between teeth as the tooth advances until a point near 91 (Fig. 6) on the flank 22 reaches the other feeler 25. The latter, together with both of the arms 42 and 43 move outwardly and to the left as viewed in Fig. 6. The accompanying outward movement of the plunger 69 upsets the electrical balance thereby causing the pointer to move outwardly from the opposite side of the centerline 87 and form the line 28a of the first mark 28, the cutter face 14 of the tooth reaching the high point on the feeler as shown in Fig.y 6 which corresponds to the outermost end of the mark. The pointer swings inwardly at 28b as the feeler 25 is allowed to move back to centered position while the cutting edge 15 is passing out of contact with the feeler. At this time, the feeler 26 will be out of contact with the next tooth.

The foregoing action is repeated as each successive tooth passes between the feelers 25 and 26 during its resultant advance along the helical line 12 by the cornbined rotary and axial movement of the hob. Thus, the feeler unit is moved alternately away from and back to the center line 87 as the cutting edges 15 and 16 of successive teeth of the hob pass between the feelers 25 and 26. By proper spacing of the feelers relative to the width of the cutting faces 14 of the teeth, the duration of the contacts between the teeth and the feelers may be made relatively short and still include the lead and other variations which are likely to occur in the regular manufacture of such cutters. By taking advantage of the tapered cross section of the hob teeth along an arcuate section line, only one of the feelers will contact the cutter at a time so that by in effect switching the control of the recorder 80 back and forth between the feelers, both sides of the teeth may be checked in a single movement of the row past the feeling unit.

Fig. 7 illustrates on an exaggerated scale some ofthe variations that may exist in a hob. If the hob teeth are perfectly formed relative to the hob axis and with the proper lead, throughout the entire length of the helical row of teeth, the points 17 on the side edges 15 and 16 at the pitch lines of each tooth will fall on lines 93 and 94 (Fig. 7) as each tooth passes the feelers 25-and 26. Such properly located cutting edges are indicated at and the marks 27 and 28 formed thereby during the testing operation will be of uniform length as indicated at 27' and 28'. If a cutting edge is located improperly with respect to either line 93 or 94 inwardly as indicated at 96 or outwardly as at 97, the feeler movement will vary correspondingly and th-e lengths of the record marks will be shortened as at 98 or lengthened as at 99.

From the foregoing, it will be apparent that if the hob teeth are perfectly formed with a uniform lead on both sides, the record marks 27 and 28 corresponding to each tooth will Ibe of equal lengths with the peaks or outer ends of all of the marks spaced equidistantly from the center line 87. By testing such a hob in -accordance with the method above described, a chart such as that shown in Fig. 15 may be obtained. In this, it will be observed that the marks on either side vary in length no more than .0003 ofan inch, a variation well within the tolerances normally allowed in precision hobs.

In the case of a right hand hob imperfectly formed witha long lead, the lengths of the marks on one side will increase progressively while correspondingly decreasing on the other side as shown in Fig. 16. Thus, for `any given tooth, the marks 27 and 28 will be of different lengths and the composite band 'formed by the two sets of marks will extend diagonally across the center line 87.

By alternately recording the positions of opposite sides of successive teeth, other defects may `be indicated. For example, if the teeth are not perfectly concentric with the hob axis, the hob will possess what is known -as run-out or eccentricity. This results in a chart such as that shown in Fig. 17 in which the marks on opposite sides of the centerline increase and decrease in a regular pattern which repeats itself in each revolution of the cutter, the two marks for the same tooth being of equal lengths. Such shaping of the chart is due to the fact that the run-out prevents the feelers 25 Vand 26 from contacting the face edges 15 and 16 at the pitch or other selected points.

Fig. 18 shows a typical chart which is produced by a hob having what is known as wobble, that is, the teeth of the helical row are not centered properly with respect to the line 12 lbut weave back and forth across this line. Such weaving is evidenced 'by the staggered relation of the bulges 91 and 92 on opposite sides of the chart center line 87.

If the hob is defective because of `both wobble and runout, the chart produced may be shaped as shown in Fig. 19.

Modified feeler arrangement v Figs. 20 and 21 show `an alternate and equivalent -arrangement of the feelers 25 and 26 for measuring the lead and other dimensional characteristics of the two cutting edges 15 and 16 in a single pass while recording these characteristics along different margins of a traveling tape. Thus, instead of feeling of opposite sides of the teeth in a `given row, or in the preferred construction described above, the feelers 25 and 26 are -arranged for coaction with the opposed flanges 21 and 22 of the different but corresponding teeth in adjacent helical rows or convolutions. These tooth flanks define the side walls of a groove whose center line 12a (Fig. 21) extends helcally around the cutter and parallels the center line 12 of each row of teeth 10.

To adapt the feelers 25 and 26 for measuring the same movements when engaging the opposed sides of different teeth of adjacent rows as when engaging opposite sides of the teeth of a single row, it is desirable for the sake of simplicity to dispose the feelers in the groove between n the adjacent rows of teeth and curve the free ends of the levers 42 and 43 so that they 'cross each other as shown in Fig. 20 and thus dispose the feelers 25 and 26 for engagement with the anks 22 and 21 respectively. In other respects, the feeler mounting is identical (see Fig. 20) in construction to that described above, the same reference :numbersv 'being eapplied- .to v'the A corresponding f pal-tsu-y ,Thus, theutwosfeelers are 1 mountedon 2 a common` support Y63tvvhich-fisgurged toward anormal `centered posi#4 tion-,determined byithe-.stop 61- and is moving clockwisefrom :this position asfthe sidefankiZZiofrone toothlengagesK thenfeeler 26 andzthe .cutting edge-151moves.past the latter' as-aillustrated in'. Fig.-21. 1 AtA thistime',i the -feelerl 25* is spacedafromfthe.opposedatooth ank 16 and does-not in- 1 terfere with the actionof thefeeler126Iin1reversing the` position .of fthe-.cutting edge. 15.

Aftenthe edge fof'oneftooth1has-passed the feeler 261,l theffeelerf-support::63..is returned toathe centered p ositionil and remains there `until the. opposednank .21s of: the-fadja+ centftoothwcomes into-.contact with the-feelerrZSas-.the cutting .edge-16; approachesfthe latter.v Aftersuch engage-f l5 ment,l theifeelerfsupport. 63?..-is swung counterclockwise until @the 'edge1l6 :passes the feeler.

Asibefore, themovements fofithenfeelers. 25 and 26Jtrans versely. oftthencenterline .12@.asethe edges 15 and 16 .ap-v proach and pass the feelers are transmittedftto .the actuatorrZO rodI .69 tof the: recording, systemiand thus .become vrecorded on= opposite1.side margins offther tapea29 intheformofi` V-.shapedamarks .-27 and .28 or so-called pips. Usually, lit is desirable .torecord the movements 27nandff28inrthe same,A positionalcrelation .as=the= edges16 kand '1S 'in the?, 25 cutter 'beingxtestedfl This may be accomplished simplybyl reversing the phase relation of the supply voltagesv appliedfz' to the; coils-:71; 73 of the sensing, and amplifying system.

An alternative and perhaps simpler :way of 'achieving the! same relation. would be to .changethe polarity of thevolt 30 tage. applied to thei penV actuating motor of thel recorder. r since in thefunitpreferably usedasabove described, this is a directcurrent'voltage with `open-terminals.

This application Vis a continuation-in-part-.of :my: appliA cation Serial,1No.l459,913 tiled October-4, 195:4, 35

I claim asy my` invention:

1. For. use inv .comparingfthe positional relation; of cutter. .teeth` arranged-:in a row extending aroundaa rotary body, each tooth .havingsides .converging toward. eachother-along saidtrow and Aawayfronrthe cutting face 40 of -the tooth,..the:combination of,-means rotatablysup porting said body.A -to advancesaidV teeth alongla predeJ temninedpathwith-the narrow ends of each tooth- :lead. ing.y they cuttingY facesfthereof; a support mounted-for movementy Vtransversely'. lofv said path -in either :direction 45 away from a predetermined centered position, means ffor sensing; amplifying-,f andrrecording Ythe successive movements of said supportraway/vfrom said centered position,` and a pair of feelers onsaid support spaced apart a xed distance less than the Width of said teeth and straddling saidfpath forengagementwith oppositesides of said vcut'- ter teeth,A saidwfeelers being.'staggered-relative to each'- other 'longitudinally of said row so that in passinggsaid" feelersfthel side anks 'of -successive `ones of vsaid VcutterY teeth-engage fthe feelersf successively and camsaid-.sup-w port outwardlyA awayy from -saidfcentered position whiley the'other feeleryis out-ofcontaet fwiththe other-side anlcof the tooth 2. For use in comparingthe positional relation'of cutter teetharranged 4in a row.'extending.aroundra;rotaryfbody, 60 eachV tooth :having sides convergingtoward'each other along said row and away from the cutting face of the tooth; the y,combination of,.means rotatably supporting said'bodyfy to advance said teeth along a predetermined path with theW cuttingffacesl trailing,v a support-mounted for ymovement transversely of ,saidfpathlin.eitherdirectionzaway from a predetermined centered position, y:means forf'serising, v amplifying, and recording the successive 4movements .of i' saidfsupportaway from said centered position,y andl a pair 1- of feelersifon saidsupportnormally. spaced apart a xed 70 distancev less than. the widthjof said cutting .faceand 1 straddling -said pathiforfengagement with opposite sides ofsaid-cutter teeth, said feelers being staggeredrelaE tive` to eachfother llongitudinally of saidrow -so that in passing said feelers the Vside-edges of the cutting `faceof 8 l successiveL ouest-of said cutter 'fteeth y'en'gagel the? feelrsf successively-Land move-'said supportI outwardly away fron!A 2- saidffc'enteredpositionwhile theother' feele' is out'foffeon: tacti withhefoppositel side of' theetoo'th". l

3 L1; For! use'dn comparing f the positional'3 Arela "onbo cutter'.'teethil'arrangedin a I-row A'extendingfaroixlid'l 'afrotary body, each "to'oth"ihavingfsideanksconverging toward gfsaid "row '-'and" away from the fcuttingl facelofiu the -too'thgflthe combinationlof, means vrotatably supporti-ng said bodylfto advance -said teethf-along apre determined path with thelf'cuttingface-trailinggla sup--- port .mounted for movement transverselyl of fsaidfpath-andi outwardly awaylfrom a predetermined l'centered posifii1;" twlo' feelersfon saidsupportnormally spaced 'aparttal dis'- gered along and straddling-said pathfforfsuccessive fenI-* gagementwith opposite sides of 'said icutter'teeth,fmeaiisf' forlsensing; :amplifying'g and "f-recordi'ng the fsuccessiv'eif movements of said lfeelers away from saidc'enteredfposi tion; and means?Y determiningl saidl'fcentered-l position "in' cluding-a4 normally? dined stop; twofv members idis'po'sedl lonl 'i opposite'fsides of S-s'aid Vs'top- `and springY urgedl tovvardanil3't norma'llyfheldfagainstfthe stop; a projection -rigidf'with-v saidlsupp'ortand.` dis'posed'lbetwe'en said-members so lthat i when: saidtfeelers `are free th'esuppor-t is heldlin saidf cen# tered positionby said member.:r`

4. Foriusewin comparing the' positionalTrelatiorrof cuttertteethv arranged ina row extending around a rotaryf' body, each'. Atooth having sides :converging-'toward' each yother along said frowandraway from the cutting'- face A*of* i the-toothg'fthel combination of, means rotatably supporting said.: bo'dyf to advance said teeth along a predetermined path with* .thecutting-L faces trailing, a support mounted" 'r for movement transversely of said path',1 two'feele'rsomsaid-.'support normally rspaced apart adistance' less than the' Width of `s'aid 'cutting faces and "staggered relative "to eachother longitudinally 'of-'said row=foreng`agement with* opposite sides' fof each 'passing toothvv successively, means urging said supporttowarda normal v'centeredl positiong" a device responsiveftotthef displacementsfof saidsupport-- away'.l from-@said normah position and operableto *convert* saidI .displacements "into `electrical f conditions vvof` propor#v tionate *magnitudes `but ofI opposite sign; -means for ampli'- fying saidwconditions; 1 a chart,`means for'y advancing-- said chart'ya recorder;lfor'formingmarks thereon, 'and means* responsiveo `vthe amplied conditions' tof actuate""said" recorder land.' form marks of 'correspondingmagnitudeion opposite side margins of'said chart.'v

5.1 For. use iincomparing the positional relation of i{cut-v ter teeth arranged in a row extendingaround a rotary body,A each'y tooth having sides `convergingtori/ard each other lalong said row andfaway fromthe cutting face'fof thel tooth;` the combination of, means :rotatably support".- ingasaidbody .to vadvance said teeth along a predeterminedi" lpath with said flcutting facesftrailingfa pairof `feelers""` normally spaced apartV4 a distance less than,the*width""of 'j saidlcutting face, means `supporting said feelers for 'mover mentin unison-'transversely of'said path 'withthefeelers straddlingsaid pathfforFenga-gement withopposite sides -ofsaidzcutterteethfpassing therebetweenysaid fee'lers and their.supporting-means having a predetermined normal" position:andfsaidlfeelersfbeingstaggered relative to 'each other longitudinally of -said'row for 'engagement with eachtootlrxsuccessivelylandioneat a time and thereby move the :feelersalterinately away-from said normal posif tiong'.` and 'means'lfor sensingand-recording'the alternate' movements' of fs'aid' fe'el'erf lsupport-ing means during'said i engagement.'

6. For use in comparing the positional relation lof fa" i plurality fof 'cutter teeth projecting from 'a rotary body and 'each having sides converging toward each other in a direction extending vcircumferentially of said body and away from the 'cutting face of the tooth, oppositely facing-iside flanks of saidteethbeing arranged in aserie's of l' pairs arranged in al helical row' withV the HanksY lof each- 9 pair spaced along an intervening predetermined path, the combination of, means rotatably supporting said body for advance of said teeth along said predetermined path with said cutting faces of the tooth trailing, a pair of feelers straddling said path and spaced apart in a direction transversely of said path a distance intermediate the spacing of said flanks at the leading and trailing ends thereof, means supporting said feelers for movement in unison transversely of said path to engage the respective tooth anks of each of said pairs as the latter pass the feelers, said feelers and supporting means having a predetermined normal position and said feelers being staggered relative to each other longitudinally of said path so as to engage each pair of tooth sides successively and one at a time whereby to move the feelers alternately in opposite directions from said normal position, and means for sensing and recording the alternate movements of said feeler supporting means during the successive engagement of the feelers with the tooth anks of each of said pairs.

7. The combination as defined in claim 6 in which said normal position of said supporting means is determined by a iixed stop coacting with two members disposed on opposite sides of said stop and spring urged toward the latter and a projection rigid with said supporting means and disposed between said members so that when said feelers are free the supporting means is held in said normal position.

References Cited in the le of this patent UNITED STATES PATENTS 

